web frameworks design comparison draft - please help me improve it focus on Model-View-Controller frameworks

Transcription

1 web frameworks design comparison draft - please help me improve it focus on Model-View-Controller frameworks

2 Controllers In Rails class MyTestController < ApplicationController def index render_text Hello World end end The name of the class has to match the name of the controller file.

3 Controllers In Django from django.http import HttpResponse def index(request): return HttpResponse("Hello World ) Django is explicit, you need to import all functions you use.

4 Controllers In Cherrypy and TurboGears 1.0 import cherrypy class def index(self): return "Hello World" Cherrypy, Turbogears, and Pylons are also explicit. You need to import all functions you want to use.

5 Controllers In web2py def index(): return "Hello World" web2py is similar to Rails. It imports for you all the web2py keyword. Often, like in this case, you do not need any.

6 Get/Post requests In Rails class MyTestController < ApplicationController def index render_text Hello +params[:who] end end GET and POST variables are passed via params but other request parameters (client ip for example) are passed via a different mechanism.

7 Get/Post requests In Django from django.http import HttpResponse def index(request): return HttpResponse("Hello World %s % \ request.request[ who ]) Nice, simple. The request contains all the info. You can use.get or.post instead of.request to be more specific.

8 Get/Post requests In Cherrypy and TurboGears 1.0 import cherrypy class def index(self,who): return "Hello %s" % who GET and POST variables are passed via arguments of the action, but other request parameters (client ip for example) are passed via a different mechanism.

9 Get/Post requests In web2py def index(): return "Hello %s" % request.vars.who Similar to Django. All request data is in one place. You can use.get_vars and.post_vars instead of.vars to be more specific.

10 Dispatching In Rails URL gets mapped into class MyTestController < ApplicationController def index render_text Hello World end end By default Rails does not allow running multiple apps without running multiple copies of Rails, since the name of the app is not in the URL, only the controller name (MyTest) and the action name (index) appear. This can be changed by configuring routes.

11 Dispatching In Django you need to edit url.py to map URLs into actions from django.conf.urls.defaults import * urlpatterns = patterns('', (r'^index$', myapp.mycontroller.index), ) This is the equivalent of Rails routes and it requires using regular expressions. There is no default. You need one entry in url.py for every action.

12 Dispatching In Cherrypy and TurboGears 1.0 import cherrypy class def index(self,who): return "Hello %s" % who Works very much like Rails and default mapping between URL and action can be overwritten.

13 Dispatching In web2py a URL like calls def index(): return "Hello %s" % request.vars.who Similar to Rails and Charrypy but, by default the URL requires that you specify the name of the app. This allows web2py to run multiple apps without using routes. Web2py has its own version of routes that supports two different syntaxes (with and without regular expression) to overwrite the mapping and reverse mapping as well.

14 Calling Views In Rails class MyTestController < ApplicationController def Hello World end end It calls the default view (MyTest/index) which renders the page. The variables marked are global vars and are passed to the view. Notice that if the view is not defined, this results in an error message.

15 Calling Views In Django from django.shortcuts import render_to_response def index(request): return render_to_response("index.html, { message : Hello World }) This is the short way of doing it in Django. You have to specify the view name index.html since there is no default. Parameters are passed via a dictionary. You get an error message if the view is not defined. Notice that in Django a view is called a template and a controller is called a view.

16 Calling Views In TurboGears 1.0 with Cherrypy import turbogears from turbogears import controllers, expose class def index(self): return dict(message= Hello World ) The view is specified in the expose decorator.

17 Calling Views In web2py def index(): return dict(message= Hello World ) The last line works like Cherrypy but by default it looks for a view called mycontroller/index.html in myapp. If this view does not exist it uses a generic view to show all variables returned in the dictionary. The default can be overwritten with response.view= filename.html

18 Views In Rails <table> do recipe %> <tr> <td><%= recipe.name %></td> </tr> <% end %> </table> It allows full Ruby in views but: - it does not escape strings by default (unsafe) - <% %> requires a special editor since < > are special in HTML

19 Views In Django <table> {% for recipe in recipes %} <tr> <td>{{recipe.name}}</td> </tr> {% endfor %} </table> The choice of {% %} and {{ }} tags is good because any HTML editor can deal with them. The code looks like Python code but it is not (notice the endfor which is not a python keyword. This limits what you can do in views.

20 Views Kid or Genshi in TurboGears 1.0 or Cherrypy <html xmlns=" xmlns:py=" <table> <tr py:for="recipe in recipes" > <td py:content= recipe.name > </td> </tr> </table> This allows full Python quotes py:for=... but it can only be used to generate HTML/XML views, not dynamical JavaScript for example.

21 Views In web2py <table> {{for recipe in recipes:}}> <tr> <td>{{=recipe.name}}</td> </tr> {{pass}} </table> Similar to Django but full Python in the code (notice pass is a Python keyword) without indentation requirements (web2py indents the code for you at runtime). Only one type of escape sequence {{ }} which is transparent to all HTML editors. All string are escaped (unless otherwise specified, like in Django and Kid). It can be used to generate JavaScript (like Django and Rails).

22 Escaping in Views In Rails <%%= message> The double %% indicate the text has to be escaped. This is off by default, hence unsafe. Should be the opposite.

23 Escaping in Views In Django {% filter safe %} {{ message }} {% endfilter %} Since Django 1.0 all text is escaped by default. You mark it as safe if you do not want it to be escaped.

24 Escaping in Views Kid or Genshi in TurboGears 1.0 or Cherrypy <div py:content= XML(recipe.name) ></div> Text is escaped by default. If text should not be escaped it has to be marked with XML

25 Escaping in Views In web2py {{=XML(recipe.name,sanitize=False)}} Text is escaped by default. If text should not be escaped it has to be marked with XML. The optional sanitize option perform XML sanitization by selective escaping some tags and not others. Which tags have to be escaped and which tag attributes can be specified via arguments of XML.

26 Views Hierarchy In Rails <title>layout Example</title> <body> <%= yield %> </body> </html> and in controller: render :layout= filename.html.erb The rendered page is inserted in the <%= yield %> tag in the layout. One can include other views with <%= render... %> Notice that also :layout follow a naming convention and there is a default.

27 Views Hierarchy In Django <title>layout Example</title> </head> <body> {% block main %} {% endblock %} </body> </html> and in view: {%block main%}body{%endblock%} Views can be extended and included using blocks that have names.

28 Views Hierarchy Kid or Genshi in TurboGears 1.0 or Cherrypy <html xmlns=" xmlns:py=" py:extends="'master.kid'">...

29 Views Hierarchy In web2py <title>layout Example</title> <body> {{include}} </body> </html> and in view: {{extend layout.html }} body Notation similar to Rails but called like in Kid. The body replaces {{include}} in the layout. layouts can extend other layouts. Views can include other views.

30 Forms In Rails <%= form_tag :action => "update" dp %> Name: <%= text_field "item", "name" %><br /> Value: <%= text_field "item", "value" %><br /> <%= submit_tag %> <%= end %> Rails has helpers to create forms but that s it. As far as I know there is no standard mechanism to automatically create forms from models (database tables). Perhaps there are Rails add-on to do this. There is a mechanism to validate submitted forms.

31 Forms In Django # in model class ArticleForm(ModelForm): class Meta: model = Article # in controller def contact(request): if request.method == 'POST': form = ContactForm(request.POST) if form.is_valid(): return HttpResponseRedirect('/thanks/') else: form = ContactForm() # An unbound form return render_to_response('contact.html', { 'form': form,}) In Django, you can create a Form (ArticleForm) from a model (Article). The Form knows how to serialize itself and validate the input on selfsubmission, but the errors are not automatically inserted in the form.

32 Forms Kid or Genshi in TurboGears 1.0 or Cherrypy? I believe you need to use a library like ToscaWidgets. Sorry, I am not familiar with them. If you know how to fill this page please let me know.

33 Forms In web2py def contact(request): form = SQLFORM(Article) if form.accepts(request.vars): redirect('thanks') return dict(form=form) This is the same as the previous Django form (generated from the Article) model, except that when the form is serialized, if there are errors, they are displayed in the form itself (unless specified otherwise). Web2py forms can also prevent double submission.

34 Validation In Rails ActiveForm::Definition::create :article do f f.section :details do s s.text_element : ,:class => 'required' do e e.validates_as_ msg => 'not ' end end Rails defines validators like requires, , etc. You can associate validators to a form. In your controllers you need to check if a form is valid, and, on error, alter the page to include the errors generated by validation.

35 Validation In Django from django.core.validators import * class Article(models.Model): = models. field( validator_list=[isvalid ]) Very much like Rails but more validators. Validators are specified in models and/or forms.

36 Validation In web2py db.define_table( Article,SQLField( )) db.article. .requires=is_ () Similar to Django and Rails because validators are attached to table fields and form fields but validators are classes not objects. This means they must be instantiated with (). You can pass arguments to the validators to change their behavior (for example the error message). The presence of validators affects the way a field is rendered in a form. For example IS_IN_SET() renders the field with a dropbox.

37 Models and Migrations In Rails class Article < ActiveRecord::Migration def self.up create_table :articles do t t.column :name, :string t.column :description, :text end end end In Rails there is a place to define tables that need to be created/deleted/ altered (migrations) and a different place to establish relations between tables (one to many, many to many, etc)

38 Models and Migrations In Django class Article(models.Model): name = models.stringfield() description = models.textfield() In Django there is one place where models are defined. If the tables do not exist they are created. Django does not do migrations (i.e. it does not alter or drop tables if the models change). For many to many relations, it creates the intermediate link table for you.

39 Models and Migrations In SQLAlchemy (used in TG and Pylons) from turbogears.database import metadata, mapper sqlalchemy import Table, Column, Integer mytable = Table('mytable', metadata, Column('id', Integer, primary_key=true)) class MyTable(object): pass mapper(mytable, mytable) SQLAlchemy makes a distinction between what tables are in the database and how they are mapped into Python objects. This is because SQLAchemy can deal with legacy databases. Rails, Django and web2py can but with limitations (in the case of web2py for example, tables must have an integer auto-increment key field called id ).

40 Models and Migrations In web2py Article=db.define_table( Article, SQLField( , string ), SQLField( description, text ) The syntax is a little different but the functionality is similar to Rails. If the the table in the model above does not exist it is created. If the model changes, web2py alters the table accordingly. One to many ad many to many relations are implied by reference fields.

41 Select Query In Rails Article.find(:first,:conditions => [ "id > :id AND name = :name", {:id => 3, :name => "test" }]) This is the most common notation for a select. The conditions argument is basically a SQL statement but the parameters are passed as additional arguments.

42 Select Query In Django Article.objects.filter(id gt=3,name= test ) id gt=3 reads id greater than 3. Django queries are lazy-evaluated.

43 Select Query In SQLAlchemy (used in TG and Pylons) query(article).filter_by(id>3, name= test )

44 Select Query In web2py db(article.id>3 and Article.name== test ).select() In web2py you always need to specify which db you are acting on because you can have multiple db connections in the same code.

45 Transcations In Rails class MyTestController < ApplicationController def index Record.transaction do... end end end

46 Transactions In Django from django.http import HttpResponse from django.db import def index(request):... return HttpResponse("Hello World ) There are multiple decorators: autocommit (commits always), commit_on_success (commit only if not Exception), commit_manually (requires calling) transaction.commit() or transaction.rollback()

47 Transactions In TurboGears import turbogears from turbogears import controllers, expose class def index(self):... return dict(message= Hello World ) By default all actions are enclosed in a transaction that commits on success and rollsback on exception.

48 Transactions In web2py def index()... return dict(message= Hello World ) By default all actions are enclosed in a transaction that commits on success and rollsback on exception.

49 Internationalization In Rails Rails currently doesn t offer any explicit support for internationalization. Perhaps it should, perhaps it s too app specific to generalize. Thinks will change in Rails 2.2 but here we talk about present, not future.

50 Internationalization In Django from django.http import HttpResponse from django.utils.translation import ugettext as _ def my_view(request): message = _("Hello World") return HttpResponse(message) Using _ is the common convention. Requires a few shell commands to build and edit the dictionaries.

51 Internationalization In TurboGears import turbogears from turbogears import controllers, expose class def index(self): message=_( Hello World ) return dict(message=message) As in the case of Django, this requires some shell commands to build and edit the dictionaries.

52 Internationalization In web2py def index() message=t( Hello World ) return dict(message=message) T is the web2py command to mark strings for translations and it differs from the others because it is not based on i18n. Dictionaries can be created and edited via the web based admin interface of web2py.

53 Helpers In Rails <%= link_to "Profile", :controller => "profiles", :action => "show", :id %> # => <a href="/profiles/show/1">profile</a>

54 Helpers In Django <a href="{%url appname.views.show_profile profile%}">profile</a> Django does not have helpers like in Rails but you can find some here:

55 Helpers In web2py {{=A( Profile,_href=URL( myapp, profile, show, args=[profile]))}} web2py has helpers but they are very different than in Rails. They are objects not functions, have the same names as the corresponding HTML tags, and can be nested as in: DIV(H1( hello,span( world ),_class= logo )) They are automatically serialized in views. _ marks tag attributes.